This invention relates to manufacturing equipment suitable for mass-production of hard capsules for medicament use.
Gelatin has been used as a thermo-gelling material of hard capsules for medicament use. However, the gelatin has problems in that it may interact with medicament ingredients and in that the control of the moisture content of capsules is troublesome for storage and handling thereof.
With an object to overcome the above described disadvantages of gelatin-made capsules, there have been proposed a methods in which cellulose ether substituted with alkyl groups or hydroxyalkyl groups is melted by heat and shaped, and in which molding pins are dipped in a solution of an organic solvent or in an aqueous solution and the solution is shaped by coating the pins with the solution.
The method of melt-shaping with heat has problems in that uniformity of the capsules can hardly be ensured and discoloration into yellow or brown may sometimes take place by the heat during shaping. The method of dipping in the organic solution has a disadvantage in that the solvent, which is toxic to humans, may remain in the capsules, in addition to the troublesome handling of the solvent. In the method of dipping in the aqueous solution, after pulling up the molding pins from the solution, the solution adhering to the pins sags down, so that it is difficult to prepare a capsule of uniform wall thickness. To improve this method it has been proposed to heat the molding pins in advance so that the solution adheres to the surface of the pin in a gelled form. But it is difficult to practice this method, because the effect is insufficient if the heating temperature is too low, while the capsule surface is often wrinkled in the course of drying if the temperature is too high.
The relation to the above-mentioned materials and methods is found in U.S. Pat. Nos. 3,493,407, 4,001,211, 2,810,659, 2,526,683 and 3,617,588.
Machines for making capsules are also found in U.S. Pat. No. 1,787,777.